1. Field of Invention
The present invention relates generally to acoustic sensors and, more particularly, to fiber optic acoustic sensors for monitoring a point in space remote from the sensor. Such monitoring is achieved by the provision of acoustic sensor for a point in space a compact and economical sensor for measuring low acoustic energy and spatially localized processes.
2. Brief Description of Related Art
Methods of measuring localized acoustic energy signals are known. For example, parabolic reflectors have been used to focus acoustic input signals on a single acoustic sensor located at the focal point of the parabolic reflector. However, parabolic reflectors receive all acoustic energy signals originating from a particular direction rather than from only a desired point of interest. Thus, unwanted noise is measured and other acoustic techniques may be required to detect and isolate the desired acoustic signals. Moreover, for a parabolic sensor to localize an acoustic signal in three dimensions the sensor must be moved so that the acoustic signals originating from a point of interest may be detected and measured from more than one location.
An array of acoustic sensors arranged in a beamformed planar array may also be used to isolate a desired acoustic process originating from a point in space by adding the desired signal in phase. However, to detect signals at reasonably high frequencies a uniform sensing surface requires a large number of sensors. Such an arrangement is limited by cost, weight and space requirements. Additionally, beamformed arrays introduce electromagnetic noise and are sensitive to electromagnetic noise. Such electromagnetic noise may originate, for example, from x-ray machines or magnetic based medical diagnostic equipment.
Thus, there is a need for a compact, economical acoustic sensor that is capable of isolating and measuring acoustic energy signals originating from a point of interest, whether that point be in air, water or a human or animal body.